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Manipulating Light on Superconducting Chips

Photonics.comMar 2013
SANTA BARBARA, Calif., March 5, 2013 — Light manipulated on a superconducting chip using a switch that shapes released photons in different waveforms could forge new pathways to building the quantum devices of the future — including superfast and powerful quantum computers.

Physicists in the lab of John Martinis, professor of physics at the University of California, Santa Barbara, have developed an unprecedented level of manipulating light on a superconducting chip, a crucial step in achieving controllable quantum devices, according to first author Yi Yin.

“In our experiment, we caught and released photons in and from a superconducting cavity by incorporating a superconducting switch,” said Yin, who worked as postdoctoral fellow in the Martinis lab from 2009 to 2012. She is now a professor at Zhejiang University in Hangzhou, China. “By controlling the switch on and off, we were able to open and close a door between the confined cavity and the road where photons can transmit. The on/off speed should be fast enough with a tuning time much shorter than the photon lifetime of the cavity.”

The switch can also be opened continuously like a shutter. This ability has allowed the investigators to shape the released photons in different waveforms — a key element for the next step they want to accomplish: controlled photon transfer between two distant cavities.

This way of moving information around — sending and catching information — is one of the most important features of the research, said co-author Yu Chen, a postdoctoral fellow in the Martinis lab. “In optics, people imagine sending information from Earth to a satellite and then back — really remote quantum communication,” he said.

“The shutter controls the release of this photon,” Chen said. “You need to perfectly transfer a bit of information, and this shutter helps you to do that.”

The method also could provide ways to transmit signals in a secure manner over long distances, said co-author Jim Wenner, a graduate student in the Martinis lab.

A schematic diagram of part of the superconducting chip used in a University of California, Santa Barbara, experiment to manipulate light for quantum communications. The wavy line is the superconducting cavity. The piece in the bottom right is the superconducting switch. Courtesy of UCSB.
Instead of another shutter, Yin used classical electronics to drive the photon, Wenner said. She then captured the signal in the superconducting cavity, in an area called the meander, or the resonator. Then the shutter controlled the photon’s release.

Wenner explained that the resonator, a superconducting cavity, is etched on the flat, superconducting chip — which is about ¼-in. square. It is chilled to a temperature of about −273.12 ºC.

A volume, bounded at least in part by highly reflecting surfaces, in which light of particularly discrete frequencies can set up standing wave modes of low loss. Often, in laser work,the resonator contains two facing mirrors that may either be flat (Fabry-Perot resonator) or have some spherical curvature, which together bind the lasing material that is referred to as the gain medium, and hence the optical cavity of a laser is where lasing occurs.